UN 2299 — Methyl dichloroacetate
Placard: Toxic. ERG Guide 156. Training/quick-reference only — use current ERG + SOP/SOG for incident-specific actions.
UN 2299 is Methyl dichloroacetate, a toxic combustible chlorinated ester assigned to ERG Guide 156. Moisture can contribute to acidic/corrosive fuming and runoff.
Hazard overview: TOXIC and combustible chlorinated ester; inhalation, ingestion or skin contact may cause severe injury. Reacts or hydrolyzes with water/moisture to form corrosive acidic products and hydrogen chloride fumes. Vapors are heavier than air and may collect in low or confined areas.
Response guidance: For a UN 2299 incident, verify the product with shipping papers, container markings, SDS and ERG Guide 156. Establish incident command, isolate the area, stay upwind, control ignition or incompatibility hazards, prevent runoff, dust or vapor spread and base entry/fire-control actions on monitoring and local SOP.
Firefighter training notes: Training for UN 2299 should emphasize corrosive fuming, moisture reaction, runoff control, Level A/B entry decisions, decontamination and incompatible materials. Use ERG 156, SDS and local SOP.
Regulatory context: Methyl dichloroacetate is regulated as a hazardous material for transportation and emergency response purposes. Storage, workplace exposure, emergency planning, spill reporting, waste handling and environmental requirements vary by exact product, concentration, quantity and jurisdiction. Verify current requirements through shipping papers, SDS, container markings and applicable DOT, OSHA, EPA, NFPA, state or local authority guidance.
Storage & handling: Methyl dichloroacetate should be stored in tightly closed compatible containers in a secure toxic/corrosive-material area with secondary containment, restricted access, ventilation and waste/decontamination planning according to SDS.
UN 2299 Quick Details
Common Hazards of UN 2299
- TOXIC and combustible chlorinated ester; inhalation, ingestion or skin contact may cause severe injury.
- Reacts or hydrolyzes with water/moisture to form corrosive acidic products and hydrogen chloride fumes.
- Vapors are heavier than air and may collect in low or confined areas.
- Combustible material: may burn but does not ignite readily.
- Fire may produce hydrogen chloride, phosgene-type gases and other toxic/corrosive smoke.
- Runoff may be acidic, toxic and corrosive.
- Containers may rupture or fail when heated or contaminated with water.
Chemical Identity & Physical Properties
Clear to pale yellow liquid with a pungent, irritating odor. Heavier than water and combustible.
| Also known as | Dichloroacetic acid methyl esterMethyl dichloroethanoateMDA |
| CAS Number | 116-54-1 |
| Appearance | Clear to pale yellow liquid with a pungent, irritating odor. Heavier than water and combustible. |
| Flash Point | 76C (169F) |
| Boiling Point | 142-144C (288-291F) |
| Vapor Density | 4.9 (heavier than air) |
| Water Reactivity | Reacts with water, releasing corrosive and toxic hydrogen chloride gas. Avoid water contact except for fire suppression. |
Fireground Response Guidance — UN 2299
Extinguishing Media
PPE Requirements
Use positive-pressure SCBA for vapor, dust, mist, fire or confined-space exposure. Wear chemical-resistant gloves, boots, eye/face protection and protective clothing selected from SDS; avoid all skin contact.
Isolation & Evacuation
First Actions for a UN 2299 Incident
- CALL 911. Then call the emergency response telephone number on the shipping paper, if available.
- Keep unauthorized personnel away.
- Stay upwind, uphill and/or upstream.
- Avoid breathing vapors, dust, mist, smoke or fumes and avoid skin or eye contact.
- Avoid unnecessary water contact with released product unless incident command confirms a compatible control use.
- Do not touch damaged containers or spilled material unless properly trained and wearing appropriate protective equipment.
- Ventilate closed spaces before entering, but only if properly trained, equipped, monitored and authorized by incident command.
- Isolate the spill or release area and expand the perimeter for fire involvement, vapor spread, dust generation, water reaction or unknown product identity.
- Use ERG Guide 156, shipping papers, SDS, air monitoring and incident command for protective actions.
📋 Copy & Share Field Card
UN 2299 — Methyl dichloroacetateUse for: Quick radio or face-to-face size-up. Short, structured, field-ready.
Use for: Incident command briefing, staging area whiteboard, or pre-entry team brief.
Use for: Quick text to command or incoming units. Fits in a single SMS.